Communicating about Cosmic Catastrophes
Brendan M. Mulligan, CIRES, Univ. Colorado (Boulder) & Queen’s Univ. (Hamilton)
Clark R. Chapman, Southwest Research Inst. (Boulder)
Introduction
The history of the Earth, and all the bodies in the solar system, has been marked by cosmic catastrophes of epic proportions: impacts due to asteroids and comets. Large-scale impacts have occurred in the past and, despite a decline in impact flux, the potential for future impacts constitutes a legitimate threat to human civilization. Communicating about the risk that near-Earth objects (NEOs) pose to the general public presents a serious challenge to the astronomical community. Although the NEO hazard has a unique character, comparisons with other natural hazards can readily be drawn and lessons can certainly be learned from years of experience that other researchers have in risk communication.
Just as specialists dealing with other hazards have done, the NEO community has addressed the challenge of risk communication by developing tools, most notably the Torino Impact Hazard Scale, capable of conveying useful information to a diverse audience. Numerous researchers and commentators have critiqued the scale, some suggesting modifications or proposing particular significant revisions. These critiques have dominantly focused on the Scale’s perceived technical weaknesses, neglecting the central issues concerning its ability to inform the public in a satisfactory way.
For instance, an issue that has already been dealt with in other cases (e.g. the “terrorism scale” of the U.S. Dept. of Homeland Security) concerns the degree to which the wording in the public scale tells people what they should specifically do in response to a particular warning level. The American Red Cross, for example, tabulated different responses that might be appropriate for different groups (individuals, families, neighborhoods, schools, and businesses) as to how they should respond to a particular level of threat. Similar clarification of the Torino Scale might be in order. We hardly expect the public to “carefully monitor” an NEO predicted as having a Torino Scale “1” close encounter; those words were intended for astronomers. But given recent hype in popular media concerning 2002 NT7, further clarification for science journalists about appropriate levels of response for different interest groups (astronomers, space agency or emergency management officials, ordinary citizens) might be appropriate.
The NT7 Event
In late July 2002, the public was alarmed when many news media carelessly proclaimed a likely threat that an asteroid would strike the Earth a few decades hence and cause terrible destruction. The route from a routine asteroid discovery, to a technically interesting but publicly insignificant prediction of an extremely low probability impact, to a headline-making scare began with the unannounced posting on technical web sites of technical data about the asteroid 2002 NT7. Included on the web sites was a ranking on a technical hazard scale (the PTS) introduced a year earlier for technical analysis (it has negative and positive numbers, and decimal places).
Although most asteroid hazard researchers had agreed to use the 1-10 Torino Scale (NT7 falling near the boundary between 0 and 1, meaning “no concern”) to communicate the seriousness of possible impact predictions, some purveyors of asteroid news (including the CCNet internet newsletter and prominent British and American news media) chose to emphasize that the NT7 event was the “first time” the PTS rating had a positive value. It was like calling the Queens air crash in autumn 2001 “the worst transportation disaster of the century” when the century was not even a year old!
CNN switched its references from the PTS to the Torino Scale in a matter of hours. But subsequent news coverage remained confusing and inappropriate to the scientific realities. If all the scientists and journalists involved in NT7 had explained (once again!) the simple process whereby new observations of the asteroid were being used to refine the predictions, which would almost certainly go to zero probability within a few days, the story might instead have run on pg. 17, or not at all. We should save the drama for truly exceptional events, conceivably even including a future impact.
Other Hazard Scales
Astronomers are hardly the first scientists to encounter difficulties with hazard scales. We can learn from experiences in developing other scales. Just as two scales have confused communication of predicted asteroid impacts, multiple scales exist for other natural hazards. But, despite internal debates about how to announce an earthquake Magnitude and the existence of multiple seismic scales, the public has been shielded from such internal, technical dissension and has become quite comfortable with Magnitudes, even though the appellation “Richter” has officially disappeared.
The RichterScale is familiar as a roughly 1-10 scale of earthquake strength. Developed by seismologist Charles Richter in the 1930s, people in California are well-calibrated to the numbers associated with their personal experiences. Educated people worldwide know that earthquakes less than 5 rarely make the news, and an 8 is something horrific. Yet there have been raging debates among seismologists, behind the scenes, about how to communicate with the public about the enormous differences between earthquakes separated by only a few numbers on the logarithmic scale. “Dare we discuss logarithms?” “What does the public understand about decimals, as in a 5.7 magnitude quake?” In reality, the Richter Scale (technically defined only for a particular instrument that saturated well below the magnitudes of large earthquakes), has been officially abandoned. Official pronouncements, at least in the U.S., refer only to Magnitude. Fortunately, “Magnitudes” are similar to values on the “Richter Scale” and the public remains blissfully unaware of the internal dissension among seismologists. Asteroid astronomers would do well to follow this example. Few members of the attentive public will put up with debates about the scales. Long-term consistency must be the watchword.
There are many other scales, some familiar and some not-so-familiar, used by different scientific specialties to translate their technical findings or judgements into mes-
sages that ordinary citizens can relate to…and take appropriate action. They deal with topics as mundane as air quality and the dangers of UV on a sunny day to topics as vital
as the end-of-the-world by nuclear war (e.g. the Doomsday Clock, of the Bulletin of the Atomic Scientists). Some other scales are esoteric; 8 separate “Space Weather Alert” scales are managed by NOAA’s Space Environment Center. Changes were made to these space weather scales in March 2002; the chief users of these scales, however, are technical people, even though there may be public consequences (e.g. with radio transmission or even electrical power). How effectively scales are presented influence their acceptance and the influence they have on behavior. The familiar fire-danger scale (arrow pointing to colored zones of fire danger ranging from “low” to “extreme”) has been used for decades and is well known in the American West. The particular illustra-
tion of the UV Index (below) is especially effective at translating the numbers into practical actions that people can take to minimize their exposure to dangerous sunlight. Some scales have been adopted internationally (e.g. the International Nuclear [Reactor] Event Scale) while others are more ad hoc.
The Torino Scale
The scale itself is a linear, 0-to-10 scale, with associated colors and words. Some critics of the scale have advocated that it be 2- or 3-dimensional. But no other hazard scales are (or should be) presented to the public in such a fashion; even educated lay people rarely comprehend 2-D graphs. The 2-dimensional plot of the Torino Scale familiar to asteroid researchers is a technical definition of how the Torino Scale values for a predicted potential impact are calculated from two quantities: the impact energy and the probability of impact. The technical version is not intended for public presentation, but for use by scientists and science communicators.
The even more complex Palermo Technical Scale (PTS) was devised for use by impact hazard experts. The scale is a one-dimensional scale (a range of numbers to several significant figures, with no beginning or end, spanning zero) calculated from the same two quantities used to calculate values on the Torino Scale plus a third quantity: the time until the predicted event.
Some have argued that the Torino Scale would be more “elegant” if it were calculated more like the PTS. In fact, there is a rough one-to-one mapping between PTS values and Torino Scale values. Indeed, the Torino Scale could be defined as = PTS +2.5 (rounded to the nearest integer, or 0 for all negative values), and its values would usually not vary by 1 unit in the important lefthand part of the diagram, or in color in the righthand part. Perhaps the definitions of the Torino Scale could be tweaked behind-the-scenes without damaging either the consistency or credibility of the scale in its public representation. In its first 4 years, the Torino Scale has gained fairly widespread use by science journalists worldwide. Its use should continue to be encouraged. Perhaps implementation of our suggestions could avoid future confusions like the one that fueled the recent NT7 media hype.
Conclusions
Clearly, the NEO community’s efforts to help the public place in context any news about possible future impacts remain only partially effective; NEO impact predictions continue to be met with confusion, misunderstanding, and sensationalism. The Torino Scale value is not the only information about impacts available to the public and, indeed, scales of any sort are not the only way to bring some convergence into public discussion of particular predictions. Astronomers have a public responsibility to develop simple protocols for honestly but understandably communicating about the inherently tiny chances of potentially huge disasters that characterize the impact hazard. Drawing from experience with other scales, we advocate that the IAU and other players and entities develop policies grounded in previous experience that can ensure accuracy, consistency, and clarity in reports of impact predictions. Only if we get our scientific house in order can we demand responsibility on the part of the science communicators and journalists who constitute the next link in the chain of communication.
Asteroid experts are not the first to face difficulties in communicating the practical implications of their work to the public. We must consistently use the Torino Scale and other simple, honest ways to put our work and predictions into an understandable context. The Torino Scale itself can be improved (both in its public image and in behind-the-scenes definitions) in ways that don’t confuse the public.